David Runciman in The Guardian:
Malcolm Gladwell's new book promises to turn your view of the world upside down. We all think we know what happened when David took on Goliath: the little guy won. Gladwell thinks we all have it wrong, and opens his new book with a retelling of that story. Our mistake is to assume it's a story about the weak beating the powerful with the help of pluck and guile and sheer blind faith. But as Gladwell points out, it was Goliath who was the vulnerable one. He was a giant, which made him slow, clumsy and probably half-blind (double vision is a common side-effect of an excess of human growth hormone). The only way he could have beaten David was by literally getting his hands on him – but David had no need to go anywhere near him. David had a sling. Ancient armies contained teams of slingers, who could be deadly from distances as great as 200 yards. The best, like David, were lethally accurate, and Goliath was not a small target. Once David had persuaded the Israelites that single combat didn't need to mean sword versus sword, but could be any weapon you like, there was only ever going to be one winner. As Gladwell says, Goliath had as much chance against David as a man with a sword would have had against someone armed with a .45 automatic handgun.
This gives Gladwell his theme. The strong are often surprisingly weak, if looked at from the right angle. People who seem weak can turn out to be surprisingly strong. Don't be a Goliath. Dare to be a David. Gladwell illustrates these lessons with a characteristically dizzying array of stories, the subjects of which range from high school girls' basketball to child murder and the Holocaust. Most of them are great stories. The trouble with the book is that they are not great illustrations of his chosen theme.